Low back disorders are a major source of morbidity, lost time, and physical disability in the workforce and represent major costs to society. Limitations to improving knowledge of preventable risk factors include costs of ensuring adequate sample sizes, restricted study populations, confounding by compensation systems and the need for detailed job task data. In addition, few studies have long-term follow-up information to determine risk factors for development of long-term disability. Through linkage of available Army databases, this cost effective study will examine and quantify the relationships of occupational, individual, and behavioral characteristics to the incidence of both low back disorders and the subsequent development of disability. The specific aims of this study are to: 1) identify occupations with the highest rates of low back hospitalization; 2) identify occupations with the highest rates of disability; 3) identify risk factors for low back hospitalization and for long-term disability; and 4) propose potential interventions based on identification of modifiable risk factors. This retrospective cohort study will follow all Army personnel between 1989 and 1997 by linking personnel, hospitalization, disability, and health risk appraisal databases by scrambled social security number. These data provide extensive information including job classification, physical job demands, medical treatment, personal factors such as smoking and exercise, job factors such as work stress and job satisfaction, social factors, and disability board evaluations. Detailed job tasks will also be examined to identify occupational characteristics placing persons at elevated risk for low back disorders. Kaplan-Meier estimates of survival function from Army entry to initial hospitalization and medical discharge for a low back disorder will be performed. Multivariate Cox proportional hazards models will be employed to determine important predictors for low back disorders. Study findings will be used to develop interventions directed at both primary prevention and at preventing development of long term disability. Benefits resulting from this study include prevention of injury and disability and large potential cost savings and will be applicable in both civilian and military settings.